This invention relates to apparatus and methods for molding aggregate blocks.
Apparatus for the mechanized molding of cement blocks are well known, as exemplified by U.S. Pat. No. 3,679,340, the disclosure of which is incorporated herein by reference.
Briefly, the molding of standard building blocks involves the introduction of moldable block material into a mold box or sleeve having fixed, straight-sided cavity walls that extend longitudinally between open top and bottom ends of the mold. A pallet is positioned to close the bottom of the cavity and a top plate, or template, overlies the top of the mold, and is formed with an opening aligned with the cavity to receive moldable block material into the cavity. The material is charged into the mold from a feed box which is moved from the side into position over the mold and discharges material through a bottom shoot, after which it is returned clear of the mold. A stripper head is lowered from above into the cavity to close the top of the mold and engage the top of the material. With the cavity closed, the mold box assembly is vibrated which, together with the weight of the stripper head, serves to compact and shape the material into the form of a block. The completed block is vertically stripped through the bottom of the mold by lowering the pallet and stripper head together, and then is conveyed onward on the pallet for further processing. The stripper head is returned and a new pallet positioned against the bottom of the cavity to ready the mold for the next cycle.
It will be appreciated that the laterally immovable cavity walls restrict the type of block that can be produced in the mold to ones having straight-sided walls or side contours that extend in the longitudinal direction of stripping. Lateral undercuts or projections are not permitted, as such would interlock the block and cavity walls in the longitudinal direction, preventing stripping.
FIGS. 2 and 3 illustrate a complex block having such lateral undercuts and projections. A mold box whose parts split laterally has been employed to form such blocks, the mold parts having the appropriate projecting and recessed mold surfaces to impart the corresponding shape to the block. The mold parts are initially inwardly displaced to provide a laterally contoured mold cavity open at its longitudinally opposite top and bottom ends. The bottom of the mold is closed by a pallet, and a top plate overlies the top of the mold and has an opening therein aligned with the open top of the mold. A feed box is moved laterally into position over the mold between the top plate and the underside of an upper stripper head to deliver the block material into the mold cavity through a bottom shoot, after which the feed box is returned clear of the mold and stripper head.
As the feed box moves into and out of position, a wire brush carried along the top of the feed box sweeps across the underside of the stripper head to remove any block material that may have accumulated from the previous mold cycle. For this particular block, the underside of the stripper head is heavily contoured. Large depending features extend into the mold and help form the projecting side features of the block as well as shaping the top surface of the block during molding.
Following compaction of the block material within the cavity, the mold parts are laterally split and retracted beneath the top plate sufficiently to disengage the mold surface clear of the block, to permit subsequent longitudinal stripping of the completed block through the bottom of the mold through conjoint downward movement of the platform and stripper head.
Some difficulties have been encountered in forming such blocks having laterally extending side features using split mold tooling of the type described above. The block material tends to accumulate on the upper surfaces of the projecting portions of the mold tooling, particularly in the inside corner regions. The material must be manually swept of blown from these regions between mold cycles, slowing the process and requiring the attendance of an operator.
The block material also tends to accumulate on the underside surface of the stripper head. The traditional wire brush carried on the feed box is unable to reach the deep inside corner features where the material is most prone to accumulate. Further, those bristles that sweep across the large projecting features of the stripper head quickly fatigue and break off.
Apparatus and method for molding blocks comprises a mold having an open top and bottom, a feedbox supported above the mold for movement into and out of position over the mold for selectively delivering a charge of moldable block material into the mold through the open top, a bottom pallet arranged below the mold for selectively closing the bottom of the mold to support the charge of moldable block material within in the mold, and a stripper head including a shoe having an underside molding surface supported for selective movement between an inoperative raised position spaced above the mold and a lowered position into the mold through the open top thereof for engaging and shaping the moldable block material with the mold. According to a characterizing feature of the invention, the feed box mounts an air knife having a nozzle supported in facing spaced relation to the underside surface of the shoe when the shoe is in the raised position. The air knife is operative during the movement of the feed box to direct a flow of high pressure air against the underside surface for cleansing the underside surface an any latent mold block material that may have accumulated between mold cycles.
The provision of the air knife has the advantage of being able to remove accumulated block material from all areas of the underside surface of the stripper shoe, regardless of whether the underside surface is flat, highly contoured, or in between. The touchless air knife cleansing system dispenses with the need for a traditional wire brush and thus avoids the problems of bristle wear and/or damage associated with the sweeping of the bristles across the underside surface of stripper shoes, particularly those which are highly contoured which quickly fatigue and break the bristles.